1. Field of the Invention
The present invention relates to a system and method for controlling engine idle in a vehicle.
2. Background Art
In a conventional wheeled vehicle having an internal combustion engine, the engine delivers torque to the wheels to propel the vehicle. When the engine is in a idling state, however, torque transfer to the wheels is interrupted. For example, when the vehicle is placed in neutral, a clutch may be used to physically disconnect the engine from the wheels, thereby resulting in zero torque transfer from the engine to the wheels.
Some vehicle architectures do not include a clutch that allows the engine to be disconnected from the vehicle wheels. In such an architecture, an alternative solution must be provided to allow the engine to idle without transferring torque to the vehicle wheels. One solution may include having a device connected to the engine that could selectively reduce its resistance to the engine torque. One example of this would be having a motor connected to the engine that could be selectively shutdown. Once shutdown, the motor would receive all of the engine torque, since the motor would provide far less torque resistance than the vehicle wheels.
This solution may be problematic, however, if immediately upon entering a neutral state, all of the torque being produced by the engine is transferred to the motor. In such a situation, the engine speed may increase to an impermissibly high level. The increase in engine speed may result in undesirably loud engine noise detected by the vehicle driver, or may be so great as to cause engine damage. Thus, there exists a need for a system and method for controlling engine idle in a vehicle when the engine maintains a direct connection to the vehicle wheels.